This is a multi-center, randomized, double-blinded, placebo-controlled, phase II/III study of the safety and anti-HCV activity of ribavarin and IFN alpha-2b as compared to IFN alpha-2b alone for the treatment of HCV disease in HIV co-infected individuals. The study has a cross-over design so that participants randomized to IFN alpha-2b monotherapy who have detectable plasma HCV-RNA at Week 12 will have ribavirin placebo replaced with ribavirin (in a blinded manner). This study is designed to observe changes in plasma HCV-RNA levels over time and sustained changes in plasma HCV-RNA in persons who are taking ribavirin with IFN alpha-2b as compared to persons taking IFN alpha-2b alone. Changes in HIV disease progression, as measured by plasma HIV-1 RNA levels, CD4+ cell count, and occurrence of AIDS defining opportunistic infections, will also be assessed. Participants' ability to tolerate potentially hepatotoxic agents, such as protease inhibitors, will also be assessed by monitoring of liver function tests (e.g. ALT).